Electrical metallic tube, coupling, and connector apparatus and method

ABSTRACT

A labor saving system, method, and apparatus for connecting or coupling lengths of electric metallic tubing (“EMT”). The invention uses couplings/connectors that have barbs that are designed to engage corresponding indentations on EMT to ensure proper installation. In one aspect, the invention is an EMT having: an EMT inner surface forming an EMT cavity; an EMT outer surface; an EMT first end; and at least one indentation in the EMT outer surface at or near the EMT first end, the indentation adapted to receive a corresponding barb from a sleeve device. In another aspect, the invention is a sleeve device comprising; a sleeve inner surface forming a sleeve cavity adapted to receive an end of an EMT; a sleeve outer surface; a first sleeve end; at least one barb on the sleeve inner surface at or near the first sleeve end, the barb adapted to engage a corresponding indentation on the EMT.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 10/425,358, filed Apr. 28, 2003, now U.S. Pat. No. 6,797,877,which claims the benefit of U.S. Provisional Patent Application No.60/360,723, filed May 15, 2002, both of which are hereby incorporated byreference in their entireties.

TECHNICAL FIELD OF THE INVENTION

This invention relates to the field of tubing. More particularly, theinvention relates to the field of electrical metallic tubing (“EMT”)apparatus including tubing, connectors and couplings, methods ofcoupling sections of EMT, and methods of connecting EMT to otherapparatus such as junction boxes or transition fittings.

BACKGROUND ART

Currently EMT is connected by using one of two methods, either a setscrew coupling or a compression coupling. The connectors are made fromeither electroplated steel or from die cast zinc. Set screw EMTcouplings are sleeves which slip over the outside diameter of twoopposing EMTs. Set screw EMT couplings typically have an inner ridge tomake sure that the two pieces of EMT butt up properly to the center ofthe coupling. The coupling has set screw(s) that penetrate the wall ofthe coupling and when tightened create both a ground path and a tightfit.

Compression couplings are made of three “body parts” plus a split glandring. The inner body is threaded on each end and then the split glandring is slipped on and then the “outer body” on each end is threadedonto the inner body. By tightening the outer body ends, the split glandring is tightened around the EMT, providing a tight fit and a goodground path.

In the installation of EMT, provisions have to be made to address theneed for a good ground path. Concerns have frequently been raised byinspectors and regulators about the integrity of the ground path ofsteel EMT. The integrity of the ground path may be degraded if the setscrews or compression sleeves are not tightened fully because electricalcontinuity relies on good, tight connections at each connection orcoupling point.

Traditional set screw connectors are basically the same as couplingsexcept one end is threaded or has some other type of attaching mechanismso that the EMT can be attached to an enclosure, such as a junction boxor some other piece of equipment that has a knock out hole of thecorrect size for the connector to fit. Connectors are usually held inplace with locknuts that lock the connector into place and provide acontinued ground path.

Existing EMT couplings and connectors require the installer to eitherturn a set screw or turn an “outer body.” The need to “tighten” a setscrew or “turn” an outer body not only requires additional work spacebut is also subject to human error, such as inadequate tightening. Ifthreaded connections are subject to vibration, the screws and/or outerbodies can loosen over time, compromising the ground path. Moreover,“twist tightening” increases the time and effort it takes for mechanicsto install EMT. Thus, a need exists for an EMT coupling and connectorsystem and method that does not require set screw or other means oftwist tightening while still providing a proper ground path.

Currently available snap fit connectors and couplings are expensive tomanufacture and provide a less than optimal ground path.

DISCLOSURE OF THE INVENTION

It is an object of the present invention is to provide EMT, connector,coupling, method for connecting, and method for coupling which are quickand efficient to install.

It is a further object of the present invention is to provide an EMT, aconnector for an EMT, and a coupling for an EMT that provides a safe andreliable ground path which does not depend on set screws being tightenedand remaining tightened.

A still further object of the present invention is to provide an EMT, aconnector for an EMT, and a coupling for an EMT that is efficient tomanufacture.

Yet another object is provide an EMT, a connector for an EMT, and acoupling for an EMT that is easy to use and capable of being used inexisting systems and equipment.

These and other objects are achieved by the present invention which inone aspect comprises an electrical metallic tube (“EMT”) comprising aninner surface forming an EMT cavity; an EMT outer surface; an EMT firstend; and at least one indentation in the EMT outer surface at or nearthe EMT first end, the indentation adapted to receive a correspondingbarb from a sleeve device. The EMT is preferably manufactured with anumber of dimples that are pressed or punched into the EMT outer surfaceclose to the EMT first end around its circumference. The number ofdimples and the distance from the EMT first end depend on the sizerequired to meet the necessary pull out tests and other criteria. Thedimples are preferably shaped like a capital D with the flat side facingthe EMT first end and the rounded side facing the center. Theindentation can also be a linearly-shaped dimple or roll groove aroundthe entire EMT outer surface so there is a continuous area for the barbsof the sleeve device to snap into. The indentation is preferably aminimal depth so as to not cause a loss in wiring capacity through theEMT cavity.

It is further preferable that the inventive EMT have an EMT second endhaving a mirror image indentation arrangement as the EMT first end.Preferably, each length of EMT will have four indentations at or neareach of its ends. Moreover, because the indentation would not be raisedabove the EMT outside surface, the inventive EMT can be used withtraditional connectors/couplings available in the market place, whichtypically slip over the outside diameter of the EMT if the inventivecouplings/connectors are not available.

In another aspect, the invention is a sleeve device for connecting EMTcomprising: a sleeve inner surface forming a sleeve cavity adapted toreceive an end of an EMT; a sleeve outer surface; a first sleeve end;and at least one barb on the sleeve inner surface at or near the firstsleeve end. The barb is adapted to engage a corresponding indentation onthe EMT described above. Depending on design needs in the field, thesleeve device can be adapted to be either a coupling or a connector byappropriately designing the opposing end of the sleeve device.

The sleeve device is preferably designed to have a C-shaped crosssectional profile and is constructed of spring steel. When the sleevedevice is used to directly receive an EMT, the sleeve cavity preferablyhas a diameter that is slightly larger than the diameter of the EMTouter surface. When the sleeve device is used in conjunction with alinking device, as discussed below, the sleeve cavity will preferablyhave a diameter that is slightly larger than the diameter of the outersurface of the linking device. The barbs are designed to slide over theEMT outer surface and “snap” into the corresponding indentations (or theroll groove) on the EMT. Preferably, the barb would point down andslightly back and will “capture” or “contact” the flat part of theD-shaped dimple or linearly-shaped dimple. If the sleeve device needs tobe removed from the inventive EMT, the sleeve device could be spun ortwisted and the barbs would free up as the spinning would result in thebarb sliding over the rounded part of the (D) or slotted depression. Itis preferred that the sleeve device have four barbs at or near its firstsleeve end for engaging four corresponding indentations on the EMT. Thebarbs help provide a ground path for the EMT by increasing the area ofcontact.

It further preferable that the sleeve device further comprise at leastone ground tab formed by a slot in the sleeve device. The ground tab canbe bent downward so that the ground tab would scrape the outer surfaceof the EMT, resulting in additional contact area. This helps to enhancethe current carrying capability and helps to maintain electricalcontinuity throughout the system.

In order to be able to use the sleeve device on cut EMT or EMTmanufactured without indentations at its ends, the sleeve devicepreferably includes a set screw locking mechanism similar to traditionalEMT set screw fittings. This allows maximum flexibility and eliminatesthe need for the field mechanic to carry two types ofcouplings/connectors. In this embodiment, the sleeve device willcomprise a set screw hole extending through the sleeve outer surface andthe sleeve inner surface for threadily engaging a set screw.

When the sleeve device is used to join two lengths of the inventive EMT,i.e., it is used as a coupling, the sleeve device will comprise a secondsleeve end having a mirror image barb arrangement as the first sleeveend. Preferably, there will be four barbs at or near the second sleeveend for engaging corresponding indentations on the second length of EMT.It is further preferable for the connection sleeve to comprise a middleinner ridge on the sleeve inner surface at or near a center of thesleeve device. By sliding the EMT into the sleeve cavity of the sleevedevice and butting it against the inner ridge, proper installation isassured.

In yet another aspect, the invention comprises a linking device for EMTcomprising: a first section having a link inner surface forming a linkcavity, a link outer surface, and at least one barb access hole adaptedto allow a corresponding barb of a sleeve device to extend therethroughwhen the sleeve device is fitted around the first section; a secondsection; and a separator between the first and second sections.

The linking device is preferably made of die-cast zinc and is designedto be used in conjunction with the sleeve device. The linking device canbe designed to couple two lengths of EMT together or can be used toconnect a length of EMT to a junction box, splice box, wireway, or otherenclosure or transition fitting.

It is preferable that the first section of the linking device furthercomprise a ground tab hole adapted to allow the ground tab of the sleevedevice to extend therethrough when the sleeve device is fitted aroundthe first section. It is also preferable that the first section comprisefour barb access holes and a set screw hole. The set screw hole shouldbe adapted to be substantially aligned with a set screw hole on thesleeve device when the sleeve device is fitted around the first section.A set screw can be extended through the set screw hole of the linkingdevice.

The linking device can also comprise an outer ridge around the outsidesurface of the first section at a first link end. This helps ensure thatthe sleeve device is properly positioned when fitted around the linkingdevice.

When the linking device is used as a connector, i.e., to connect alength of EMT to a junction box or other transition fitting, it ispreferable that the second section be adapted to do so by incorporatinga threaded outside surface or a snap fit assembly on the second section.

When the linking device is used as a coupling, i.e., to connect twolengths of EMT, the link cavity extends through the second section sothat the second section has a link inner surface and a link outersurface that mirrors the first section. In this embodiment, the secondsection will have at least one barb access hole, at least one ground tabhole, and at least one set screw hole.

In still another aspect, the invention is a connection assembly for EMTcomprising a combination of the linking device and the sleeve device,wherein the sleeve device is fitted around the first section of thelinking device so that the barb on the sleeve device extends through thebarb access hole of the linking device. By varying the design of thesecond section of the linking device, the connection assembly can beused to couple two lengths of EMT or connect a single length of EMT to ajunction box or other transition fitting.

In a still further aspect, the invention is an EMT joint assemblycomprising: an EMT having an EMT inner surface forming an EMT cavity, anEMT outer surface; an EMT first end, and at least one indentation in theEMT outer surface at or near the EMT first end, the indentation engaginga corresponding barb from a sleeve device; the sleeve device having asleeve inner surface forming a sleeve cavity adapted to receive an endof the EMT, a sleeve outer surface; a first sleeve end; and at least oneof the corresponding barbs on the sleeve inner surface at or near thefirst sleeve end. The EMT joint assembly is preferably constructed asdiscussed above.

In another aspect, the invention is a method of connecting EMT. Whenused to connect cut EMT or EMT manufactured without indentations at itsends, the method comprises: providing an EMT having an inner surfaceforming an EMT cavity, an EMT outer surface, and an EMT first end;providing a sleeve device having a sleeve inner surface forming a sleevecavity adapted to receive the EMT first end, a sleeve outer surface, afirst sleeve end, and at least one barb on the sleeve inner surface ator near the first sleeve end; and inserting the EMT into the sleevecavity.

When used to connect or couple EMT having at least one indentation inthe EMT outer surface at the EMT first end, the barb will engage theindentation when the EMT is inserted into the sleeve cavity. Preferably,a ground tab on the sleeve device will be bent inwardly to contact theEMT. Moreover, the inventive method can be used to connect the EMT andsleeve device to a junction box or transition fitting through the use ofa linking device, as described above.

The present invention significantly reduces the time required forelectricians and installers to connect EMT and addresses a serioussafety concern often raised regarding the installation of EMT. Thepresent invention eliminates the time-consuming complexity of theexisting connection methods by allowing the EMT to simply snap togetherwhile providing improved and more reliable ground paths. The inventionoffers the installer the option of using the new labor saving fittingsor to continue to use traditional fittings with no loss in installationtime or performance. Moreover, the loss of interior wire fill space willbe insignificant. The installed cost of the raceway system will besignificantly reduced while, most importantly, the concerns of poorworkmanship resulting in poor ground path and potential safety hazardswill be extremely reduced or eliminated.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of an embodiment of a length of EMT havingD-shaped indentations.

FIG. 2 is a front view of the EMT of FIG. 1 along line II—II.

FIG. 3 is a perspective view of a portion of the EMT of FIG. 1.

FIG. 4 is a side view of an end portion of an EMT having linearly-shapedindentations.

FIG. 5 is a is a side view of an embodiment of a sleeve couplingaccording to the present invention.

FIG. 6 is a front view of the sleeve coupling of FIG. 5 along lineVI—VI.

FIG. 7 is a perspective view of a portion of the sleeve coupling of FIG.5.

FIG. 8 is a side view of an embodiment of a linking device adapted toconnect a length of EMT to a junction box according to the presentinvention.

FIG. 9 is a front view of the linking device of FIG. 8 along line IX—IX.

FIG. 10 is a perspective view of the linking device of FIG. 8.

FIG. 11 is a side view of an embodiment of a linking device adapted toconnect two lengths of EMT according to the present invention.

FIG. 12 is a side view of an embodiment of a connection assemblycomprising the linking device of FIG. 8 and a sleeve half.

FIG. 13 is a front view of the connection assembly of FIG. 12 along lineXIII—XIII.

FIG. 14 is a side view of an embodiment of an EMT joint assemblycomprising the sleeve coupling of FIG. 5 connecting two lengths of theEMT of FIG. 1.

MODES FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1–3, an embodiment of a length of EMT is illustratedaccording to the present invention. EMT 10 has tubular shape and acircular cross-sectional profile. EMT 10 can be constructed of steel,alloys, aluminum, or any other metal or material capable of carryingelectricity. EMT 10 has an outer surface 13 and an inner surface 14. EMT10 has EMT first end 11 and EMT second end 12. Inner surface 14 formsEMT cavity 15 extending through the length of EMT 10 for holding wire.

EMT 10 further comprises indentations, in the form of D-shaped dimples16, at both EMT first end 11 and EMT second end 12. Each of the D-shapeddimples 16 are adapted to receive and engage a corresponding barb 25 ofsleeve device 20 (FIGS. 6 and 7). EMT 10 comprises four D-shaped dimples16 circumferentially located around each of its ends 11, 12. D-shapeddimples 16 are formed in outer surface 13 by punching or pressing andpreferably have a depth of approximately one-eighth inch. EMT 10 is oneand one-half inch EMT pipe (i.e. one and one-half inch diameter) but cantake on any size and still be within the scope of the present invention.

D-shaped-dimples 16 are located a distance A from EMT first and secondends 11, 12. Distance A is substantially equal to distance B, thedistance that barbs 25 are located from middle inner ridge 27 of sleevedevice 20 (FIG. 5). D-shaped dimples 16 also correspond to thecircumferential orientation of barbs 25 on sleeve coupling 20 (FIG. 5).

Referring now to FIG. 4, EMT 17 is illustrated according to a secondembodiment of the present invention. In this alternative embodiment, EMT17 has four linearly shaped grooves 18 in outer surface 13 instead ofthe D-shaped dimples 16. Similar to D-shaped dimples 16, linearly shapedgrooves 18 are adapted to receive and engage a corresponding barb 25 ofsleeve coupling 20 (FIGS. 6 and 7). While two examples of theindentation on outer surface 13 have been illustrated, those skilled inthe art will appreciate that the indentation(s) can take on almost anyshape or size, including a roll groove that extends around the entirecircumference of outer surface 13.

FIGS. 5–7 illustrate an embodiment of a sleeve coupling according to thepresent invention. Sleeve coupling 20 is designed to be used to connecttwo lengths of EMT 10 (as shown in FIG. 14). However, those skilled inthe art will appreciate that sleeve coupling 20 can be modified to be aconnector, which can be used a single length of EMT to a junction box orany type f transition fitting.

Sleeve coupling 20 comprises a first sleeve end 21 and a second sleeveend 22. Sleeve device 20 is constructed of spring steel and has aC-shaped cross sectional profile (visible in FIG. 6). The C-shapedcross-sectional profile and the steel spring construction allow sleevecoupling 20 to be easily fitted around EMT 10 (FIG. 14) without damagingbarbs 25. Sleeve coupling 20 has an inner sleeve surface 23 and an outersleeve surface 24. Inner sleeve surface 23 forms sleeve cavity 26, whichextends the length of sleeve coupling 20. Sleeve cavity 26 is sized andshaped so as to be capable of receiving one of the EMT ends 11 or 12 ofEMT 10 (FIG. 1). Sleeve coupling 20 preferably comprises a middle innerridge 27 on inner sleeve surface 23 near the center of sleeve coupling20. Middle inner ridge 27 acts a “stop” for EMT that is inserted intosleeve cavity 26.

Sleeve coupling 20 further comprises four barbs 25 at each of its sleeveends 21, 22. The barb arrangement on second sleeve end 22 is the same asthe barb arrangement on first sleeve end 21. Barbs 25 are formed bypunching or pressing the steel and bending the barbs inward and back.Optionally, the steel will be heat tempered thereafter. Barbs 25 aredesigned to slide over the EMT outer surface 13 and “snap” intocorresponding D-shaped dimples 16 (FIG. 1). Preferably, the barbs willpoint down and slightly back and will “capture” or “contact” the flatpart of the D-shaped dimple 16 (FIG. 1).

Sleeve coupling 20 also has ground tab 28. Ground tab 28 is formed by apunched or pressed slot. Ground tab can 28 can be bent inward alongdotted line 29 so that ground tab 28 will contact EMT outer surface 13when EMT 10 is positioned in sleeve cavity 26 (as illustrated in FIG.14). This helps to enhance the current carrying capability and helps tomaintain electrical continuity throughout the system.

Sleeve coupling 20 further comprises set screw hole 30 having set screw31 threadily engaged therethrough. Set screw 31 is preferably ahex-shaped screw. This set screw feature allows sleeve device 20 to beused in conjunction with cut EMT or EMT manufactured withoutindentations at its ends. This allows maximum flexibility and eliminatesthe need for the field mechanic to carry two types ofcouplings/connectors.

Sleeve coupling 20 can be modified to be a connector to be used toconnect a length of EMT to a junction box or other transition fitting.In the connector embodiment, the second sleeve end will be adapted toconnect to a junction box or other transition fitting by modifying theouter sleeve surface near the second sleeve end to be threaded or byincorporating a snap fit assembly. In this embodiment, the second sleevesection will be solid and be constructed similar to second link section42 shown in FIG. 8.

Referring now to FIGS. 8–10, linking connector 40 is illustrated.Linking connector 40 has first section 41 and second section 42. Firstsection 41 and second section 42 are separated by hex-shaped separator43. Separator 43 not only acts to separate sections 41 and 42 but canalso be used to turn linking connector 40 if necessary.

First section 41 has a link outer surface 44 and a link inner surface45. Link inner surface 45 forms link cavity 46. Link cavity 46 is sizedand shaped to receive one of end 11, 12 of EMT 10. First section 41further comprises four barb access holes 47 and two ground tab holes 48.Barb access holes 47 are sized and positioned on first link section 41so as to allow a corresponding barb 25 of sleeve half 60 to extendtherethrough when sleeve half 60 is fitted around first link section 41,as shown in FIGS. 12 and 13. Similarly, ground tab holes 48 arepositioned and sized to allow a corresponding ground tab 28 of sleevehalf 60 to extend therethrough when the sleeve half 60 is fitted aroundfirst link section 41, as shown in FIGS. 12 and 13. First section 41also has set screw hole 49. Set screw hole 49 is adapted to allow setscrew 50 to extend therethrough (FIG. 12). Set screw 50 is preferably ahex-shaped screw. Alternatively, set screw hole 49 can be a threadedhole so as to threadily engage set screw 50. When set screw hole 49 isthreaded, is not necessary that set screw hole 30 on half sleeve 60 bethreaded (FIG. 12).

Finally, linking connector 40 comprises a first link end 51 and a secondlink end 52. First section 41 preferably has outer ridge 53circumferentially located on outside surface 44 at or near first linkend 51. Outer ridge 53 helps ensure that sleeve half 60 is properlypositioned on first section 41 when it is fitted around linkingconnector 40, as illustrated in FIG. 12.

Second section 42 of linking connector 40 is adapted to engage ajunction box or other transition fitting (not illustrated). This is doneby threading outside surface 54. Alternatively, a snap fit assembly orany other connection means can be incorporated into second section 42.

It is possible to adapt the linking connector concept described above tobe a coupling used to connect two lengths of EMT. Referring now to FIG.11, link coupling 70 is illustrated. As with linking connector 40, linkcoupling 70 comprises a first section 71 and a second section 72. Linkcoupling 70 also comprises hex-shaped separator 73. First section 71 isdesigned similar to first section 41 of linking connector 40, comprisingbarb access holes 77, ground holes 78, and set screw hole 79. Howeversecond section 72 is also designed to engage one of the ends 11 or 12 ofa second length of EMT 10. This is done by making second section 72 amirror image of first section 71. As such, second section 72 is alsoadapted to have a half sleeve 60 fitted around it.

Referring now to FIGS. 12 and 13, connection assembly 80 is illustrated.Connection assembly 80 comprises linking connector 40 and half sleeve60. Linking connector 40 is described in detail above in relation toFIGS. 8–10. Half sleeve 60 is one half of sleeve connector 20, which isdescribed in detail above. As such, a detailed explanation of thestructure of these components will be omitted. Only the structuralcooperation between half sleeve 60 and linking connector 40, when fittedtogether, will be discussed.

Half sleeve 60 has a C-shaped cross-sectional profile and is made ofspring steel. Half sleeve 60 is sized and shaped so that it fits aroundfirst section 41 (FIG. 8) of linking connector 40. Outer ridge 53 helpsensure that half sleeve 60 is properly positioned. When half sleeve 60is fitted around first section 41 (FIG. 8), the four barbs 25 of halfsleeve 60 extend through corresponding barb access holes 47 of linkingconnector 40 (best visible in FIG. 13). As such, an end 11, 12 of EMT 10(FIG. 1) can be inserted into link cavity 46 so that the barbs 25 willengage corresponding dimples 16 (FIG. 1).

Set screw hole 49 of linking connector 40 is substantially aligned withset screw hole 30 of half sleeve 60. Set screw 50 can then be extendedthrough and threadily engage both set screw holes 49 and 30. When an end11, 12 of EMT 10 (FIG. 1) is inserted into link cavity 46 and set screw50 is incorporated, set screw 50 will contact the outer surface 13 ofEMT 10 (FIG. 1). This will help form a ground path and secure the EMT 10in place. As discussed earlier, the use of a set screw is not necessaryand is preferably only used when the EMT end does not have indentations.

Additionally, ground tab holes 48 of linking connector 40 aresubstantially aligned with ground tabs 28 of half sleeve 60. Ground tabs28 can be bent inward to extend through ground tab holes 48. When an end11, 12 of EMT 10 (FIG. 1) is inserted into link cavity 46 and groundtabs 28 are bent inward, ground tabs 28 will contact the outer surface13 of EMT 10 (FIG. 1).

Referring now to FIG. 14, EMT joint assembly 90 is illustrated. EMTjoint assembly 90 comprises sleeve coupling 20 operably coupled with andconnecting two lengths of EMT 10. The structure of sleeve coupling 20and EMT 10 are discussed in detail above. When sleeve coupling 20 isused to couple two lengths of EMT 10, one of the ends 11, 12 of each EMT10 is inserted into sleeve cavity 46 from opposite sides until they buttagainst inner ridge 27 (FIGS. 5–7).

When fully inserted into sleeve coupling 20, barbs 25 engagecorresponding dimples 16 of EMTs 10, locking them in place. Set screws31 are tightened so as to contact the EMTs 10. The use of a set screw isnot necessary and is preferably only used when the EMT end does not haveindentations. Ground tabs 28 are either bent inward so as to contact theEMTs 10 or can be pre-bent.

Alternatively, sleeve coupling 20 can be used to couple EMTs that do nothave indentations or dimples. Additionally, if sleeve coupling 20 isreplaced by connection assembly 80 (FIG. 12), a single length of EMT 10can be connected to a junction box or other transition fitting.

While the invention has been described and illustrated in sufficientdetail that those skilled in this art can readily make and use it,various alternatives, modifications, and improvements should becomereadily apparent without departing from the spirit and scope of theinvention.

1. An electrical metallic tube (“EMT”) having: an EMT inner surfaceforming an EMT cavity; an EMT outer surface; an EMT first end; and atleast one indentation in the EMT outer surface at or near the EMT firstend, the indentation adapted to receive a corresponding barb from asleeve device, wherein the indentation(s) are pre-manufactured and, whenviewed from the outer surface, are either of a D-shape or are of alinear shape, the linear shape being parallel to the first end.
 2. TheEMT of claim 1 comprising four of the indentations at or near the EMTfirst end.
 3. The EMT of claim 1 further comprising an EMT second endhaving the same indentation arrangement as the EMT first end.
 4. The EMTof claim 3 comprising four of the indentations at each of the first andsecond EMT ends; wherein the indentations are D-shaped dimples; whereinthe dimples are pre-formed by pressing or punching the EMT outer surfaceduring the manufacture of the EMT.
 5. The EMT of claim 1 wherein theindentation is a distance from the first end that is substantially equalto a distance from a barb of a sleeve device to a stop of the sleevedevice.